The skin is a very important tissue that protects the human body in direct contact with the external environment and has biochemical and physical functions. Skin tissue is broadly divided into three parts: epidermis, dermis and hypodermis. Human skin color varies mainly depending on the number, size, type and distribution of melanosomes containing melanin within skin cells. The melanosomes are produced by melanin cells, and melanin is a black pigment produced in epidermis and is produced in melanocyte cells.
Melanin functions to protect deeper cells from UV light damage by absorbing UV light energy from sunlight. However, if the melanin is abnormally reduced, skin lesions, such as vitiligo, will occur, and on the contrary, if excessive melanin synthesis by UV and the like will damage the skin and form discolorations and freckles that can also cause skin cancer.
Human skin color is determined by various factors, among which the activity of melanocytes making melanin pigments, the distribution of blood vessels, the thickness of the skin, and whether the human body contains pigments, such as carotenoid and bilirubin, are important factors. Particularly, the most important factor is black pigment melanin that is produced by action of various enzymes, such as tyrosinase, in human melanocytes. The formation of this melanin pigment is influenced by physiological factors associated with, for example, genetic factors, hormone secretion and stress, and environmental factors such as UV light irradiation.
However, the excessive production and deposition of the melanin pigment cause skin abnormalities, such as skin darkening, discoloration, freckles and pigmentation. For this reason, in order to treat or reduce excessive melanin pigmentation caused by UV light exposure, ascorbic acid, kojic acid, arbutin, hydroquinone, glutathione or derivatives thereof, or substances having tyrosinase inhibitory activity, have been used in cosmetics or medical drugs, but have limited usability due to insufficient whitening effects, the problem of safety to the skin, and the problems of formulation and safety in cosmetics.
Recently, studies to find whitening active ingredients from natural substances have been continued. Among these ingredients, pluralities of plants extracts, including Souhakuhi extracts (Korean Patent Laid-Open Publication Nos. 99-002109 and 97-021273) were found to act on tyrosinase so as to inhibit the production of melanin. However, these extracts also have many problems in use at effective concentrations or higher in terms of stability, safety and discoloration possibility, and do not exhibit satisfactory effects.
Particularly when these whitening compositions are used in combination with a pack, they will be kept in direct contact with the skin for a given period of time because of the characteristics of the pack. Thus, they have disadvantages in that they will damage the soft skin or have an insufficient effect on restoration to a healthy and glossy skin, and in a severe case, artificial synthetic pack compositions can cause side effects, such as skin rashes or allergy. For this reason, attempts to use natural substances having moisturizing effects and excellent whitening effects in pack products have recently been increased.
Korean Patent Laid-Open Publication No. 2003-0039389 discloses a cosmetic composition for packs, including herbal and natural extracts. But, these natural substances do not have satisfactory skin whitening effects, and therefore, the development of a natural substance having satisfactory skin whitening effects is required.
Accordingly, the present invention have conducted to develop a whitening composition for packs, which has high skin whitening effects without causing any side effect on the human body, particularly the skin, due to the use of a natural substance, so that, when it is used as a general functional cosmetic composition or particularly used in packs, it will show surprising skin whitening effects, and at the same time, be safe for the skin. As a result, we have completed the present invention.